Static protective apparatus.



R. P. JACKSON.

STATIC PROTECTIVE APPARATUS APPLICATION FILED JULY 29 l9|3 Patented July 2, 1918.

, INVENTOR ATTORNEY UNITED STATES PATENT OFFICE.

RAY P. JACKSON, OF EDGEWOOD PARK, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC AND MANUFACTURING COMPANY, ACORPORATION OF PENNSYLVANIA.

STATIC PROTECTIVE APPARATUS.

Application filed July 29, 1913.

To all whom it may concern:

Be it known that I, RAY P. JACKSON, a citizen of the United States, and a resident of Edgewood Park, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Static Protective Apparatus, of which the following is a specification My invention relates to devices for protecting electrical circuits and electrical ap.

paratus from injury by reason of lightning discharges, static disturbances and strains that are occasioned by the flow of high-frequency currents.

My invention relates particularly to devices by means of which the energy sustaining the flow of high-frequency currents in the disturbed circuit, is absorbed and dissipated as heat.

One object of my invention is to provide a means for protecting electrical circuits and the apparatus associated therewith against high-frequency currents, which means is effective against currents of extremelywide ranges of frequency.

Another object of my invention is to provide a protective means for eliminating the danger occasioned by the flow to ground of dynamo currents which tend to follow in the paths of the arcs established by the discharge to ground of high frequency currents.

A further object of my invention is to provide electrical circuits with an efficient protective means against high-frequency currents, which means does not necessitate periodical inspections and renewals, and which may be easily inserted in the electrical circuit without any additional supporting structure and the usual and unreliable ground connections.

For a better understanding of the nature, the scope and the characteristic features of my invention, reference may be had to the following description and the accompanying drawing forming a part hereof in which Figure 1 is a side view, partially in section, of a device constructed in accordance with my invention; Fig. 2 is an end view of the device shown in Fig. 1, and Fig. 3 is a view of a structure embodying a form of my invention.

Referring to Fig. 1, a choke coil 1 of a standard type of construction is adapted to be inserted in series with a conductor 2 of a transmission line. Projecting through the Specification of Letters Patent.

Patented July 2, 1918.

Serial No. 781,758.

choke coil 1, and electrically connected to the terminals 3 thereof, is a non-inductive resistance element, preferably in the form of a resistance rod 1. Between each pair of wooden strips 5 is disposed an insulating body 5 which insulates the turns of the choke coil from one another and retains them in fixed relation to one another, thereby assuring rigidity to the coil. In order that all the mechanical tension transmitted from the sections of the conductor 2 may not distort the choke coil 1, a strain insulator 6, preferably in the form of a tube surrounding the resistance rod 4, is connected between the terminals 8 of the choke coil. the strain insulator thus assuming the mechanical tension existing between the sections of the conductor.

The choke coil 1 is preferably made from an aluminum rod wound in the form of a helix, the end turns of which have inwardly and radially extending portions 7. Secured to each of the extending portions 7, and electrically connected thereto, is the metallic terminal 3. The terminals are provided with recessed portions 8 by means of which each section of the conductor 2 may be securely connected to its respective end turn of the coil 1. Other recessed portions 9, integrally formed upon the terminal 3, provide means for gripping the extremities of the strain insulator 6. The mechanical tension existing between the several sections of the con-' ductor 2, by reason of the insertion of the device of my invention, is assumed by the said insulator, thus relieving the choke coil proper and the resistance rod 4 from all mechanical strains. This type of construction prevents the distortion of the choke coil and maintains it in its initial form. It will be noted that the choke coil 1 is spaced from the strain insulator 6 and its associated elements in order that an air space may intervene therebetween to preclude the establishing of a leakage path between the terminals of the coil or adjacent turns of the coil.

When high-frequency disturbances occur upon the conductor 2, they will travel from one end to the other end of the said conductor until the energy sustaining them is dissipated. If the potential of these disturbances is of a sufliciently high value, they will discharge to ground through the apparatus connected to the conductor 2 unless provision is made for otherwise relieving the said conductor of the strains occasioned by these traveling disturbances. In order to protect the connected apparatus from the high-potential disturbances occurring upon a conductor, it is usual to insert between the said apparatus and the associated transmission conductor, protective devices which afford a comparatively easy path of discharge to ground for these disturbances. A common form of such protective means is a choke coil in combination with spaced members forming an air gap, an electrolytic condenser, and a ground connection, the said protective means being well known in the art and, therefore, requiring no explanation relative to its operation. 1

In my invention, I have combined a choke coil 1 with the resistance element 4 which is connected in shunt relation therewith. I prefer that the resistance rod 4 be made of carborundum, which material is cheap and durable and has a hi h specific resistance. The rod 4 is inclosed by the strain insulator 6 which prevents the rod from absorbing water when exposed in the open air. As shown, the extremities of the rod 4 project into recessed portions 9 whereby electrical connection is established with terminals 3 of the choke coil.

A high-frequency disturbance occurring upon the conductor 2 will flow uninterrupt edly. until it encounters the choke coil 1. Because of the self induction of the choke coil, the high-frequency currents are reflected and prevented from flowing across it. The flow of these high-frequency currents being thus obstructed, they will pass through the non-inductive resistance element 4 which offers to them a high-resistance path around the choke coil 1. As the currents flow through the rod 4, the energy sustaining them is absorbed by the rod and is transformed into heat which is readily dissipated,

thus relieving the conductor 2 from the strains occasioned by the high-frequency disturbance.

The electrical constants of the choke coil 1 and the resistance element 4 should be so related as to dissipate at a high rate, the energy sustaining the high-frequency disturbances. I have found that the maximum amount of energy which sustains the electrical currents of a given frequency is absorbed and dissipated as heat by the resistance rod 4 when the resistance offered by the said resistance element to the flow of the dis turbances is numerically equal to the reactance offered thereto by the choke coil 1.

To illustrate the applicability of my invention, assume a choke coil of a standard type of construction, the choke coil having a coefficient ofself induction equal to .000,207 henrys. The reactance offered by the said coil to a current having a frequency of 150,000 cycles will be approximately 200 turbance will be absorbed if the resistance of the rod 4 numerically equals the reactance offered by the choke coil 1 to the said disturbance, namely, when the resistance of the rod 4 is approximately 200 ohms. I have found that, if the ohmic resistance of the rod 4 varies 50% below or 100% above 200 ohms or the value at which the maximum amount of energy is absorbed, the watt or energyabsorbing function of the said resistance rod is reduced only 25%. This characteristic of my device permits it to absorb power efiectively within 25% of the maximum amount of power when the frequency of the disturbing currents ranges from 7 5,000 cycles to 300,000 cycles.

In Fig. 3 is shown a combination of three devices embodying my invention, connected in series, each device comprising a choke coil 1 shunted by a resistance rod 4, substantially as described relative to the protective device shown in Fig. 1. I prefer that the coefficient of self induction of each of the coils 1 be of the same value although this to have a coefficient of self induction equal to 000,207 henrys. Connected in shunt relation with one coil is a rod 4 having an ohmic resistance of 200 ohms which absorbs the maximum. amount of power when the disturbing currents have a frequency of 150,000. cycles. The combination with the second choke coil has a rod having an ohmic resistance of 600 ohms which absorbs the maximum amount of power when the disturbing currents haveafrequency of 450,000 cycles, and the third choke coil is shunted by a rod having an ohmic resistance of 1200 ohms which absorbs the maximum amount of power when the disturbing currents have a. frequency of 900,000 cycles. As hereinbefore mentioned, the watt or energy-absorbing power of each of the said resistance rods is reduced only 25% when the frequencies vary from 50% below to 100% above the normal frequency of the disturbing currents. By reason of this, the device comprising the three choke coils and their associated resistance rods is adapted to afford elfective protection when the frequencies of the disturbances vary from 75,000 to 1,800,000 cycles. It may readily be seen that this characteristic, which adapts my protective means to such an extremely wide range of frequency, assures ample and effective protection from all disturbances that may occur upon the cooperating conductor.

It is apparent from the foregoing description that no ground connections are necessary for dissipating the energy which sustains the disturbances upon the conductor. This eliminates the danger which will accrue to the generating apparatus connected thereto by reason of the flow of dynamo currents in the paths of discharge of the high-frequency currents to ground. As the device of my invention has no parts which rapidly deteriorate or need periodical inspection, the cost of upkeep, as well as the cost of installation, is negligible.

I have shown a choke coil which is wound in the form of a helix, but choke coils having different forms may be used with equal effectiveness, the essential requisite being that the reactance offered by the inserted choke coil to the line currents, which have an extremely low frequency relative to that of lightning disturbance, be negligible so as to maintain the efiiciency of transmission of the power current to a high and economical value.

IVhile I have herein described several embodiments of my invention, it is not intended that my invention in all its aspects shall be limited to these particular embodiments, as it will be apparent to anyone skilled in the art that many changes may be made in the form of my invention without departing from the spirit thereof.

I claim as my invention:

1. A protective device comprising a choke coil, a high-resistance and non-inductive element, and a strain insulator providing a housing for said resistance element, the insulator being positioned axially in said choke coil and mechanically connected to the end turns thereof.

2. A protective device comprising a choke coil, a resistance element electrically connected in shunt therewith, and a strain insulator providing a housing for said resistance element and mechanically connected to Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents the end turns of the choke coil to assume the mechanical strains which may be transmitted to the said protective device.

3. A protective device adapted to be inserted between adjacent sections of an electrical conductor, said device comprising a choke coil, a resistance element in shunt relation therewith, and a strain insulator housing said resistance element, said strain insulator providing means for transmitting the mechanical tension existing between the said sections of the conductor.

4;. A protective device comprising a group of inductive resistance elements connected in series with each other, and a group of noninductive resistance elements each of which is associated with its respective inductive resistance element, the similar elements comprising one of said group having the same electrical constants and the similar elements comprising the other of said groups having electrical constants which progressively increase in amounts.

5. A protective device comprising a plurality of choke coils which have substantially the same co-efiicient of self induction, and a plurality of resistance elements each of which is connected in shunt relation with its respective choke coil, the ohmic resistance of each of the resistance elements varying from that of the others.

6. A protective device comprising a choke coil the turns of which are spaced from one another, a strain insulator mechanically connected to the end turns thereof and a resistance element electrically connected in shunt to the choke coil and housed in said strain insulator, the choke coil and strain insulator being spaced from each other to provide an air space therebetween.

In testimony whereof, I have hereunto subscribed my name this 17th day of July, 1913.

RAY P. JACKSON.

Witnesses GoLDIE E. MoGEE, B. B. Hnvns.

Washington, I). 0. 

